Experts say promoters inflated estimates of the cost of providing alternatives if the rail system isn't built.

As the price tag for California's bullet train has soared to nearly $100 billion, a central argument for forging ahead with the controversial project is an even loftier figure: the $171 billion that promoters recently estimated will be needed for new roads and airports if no high-speed rail is built.

Without a fast-rail network, they warn, the state would have to add 2,300 miles of highway and roughly the equivalent of another Los Angeles International Airport to handle a projected surge in future travel.

Now, that alternative is coming under attack by a state-appointed panel of experts, who will soon release an assessment of the rail project's business plan and cast doubt on the accuracy and validity of the $171-billion figure, The Times has learned.

Already, transportation researchers, government officials and watchdog groups are saying the $171-billion claim is based on such exaggerated estimates, misleading statements and erroneous assumptions that it is "divorced from any reality."

For The Record Los Angeles Times Wednesday, January 18, 2012 Home Edition Main News Part A Page 4 News Desk 1 inches; 45 words Type of Material: Correction Parsons Brinckerhoff: An article in the Jan. 17 LATExtra section about cost estimates developed by the California High-Speed Rail Authority identified a consultant as Parsons Brinkerhoff. The New York-based firm's name is spelled Parsons Brinckerhoff. Also, the firm is not connected to Pasadena's Parsons Corp.

"There is some dishonesty in the methodology," said Samer Madanat, director of UC Berkeley's Institute of Transportation Studies, the top research center of its type in the nation. "I don't trust an estimate like this."

Until November, California High-Speed Rail Authority officials were asserting that the alternative cost of highway and airport construction would be $100 billion. Earlier predictions were billions lower. When the estimate for the bullet train project recently hit $98.5 billion, the authority ratcheted the highway and airport cost up to $171 billion.

The price of alternatives is a central part of the authority's rationale for building the high-speed rail network, along with jobs and possible environmental benefits. The bullet train is aimed at meeting future transportation needs of the state, which cannot be economically met with highways and airports, the authority says.

"If anything, we underestimated the costs of alternatives to high-speed rail," said Dan Richard, an authority board member who is in line to become the group's chairman. "Expanding freeways and then maintaining them is not a free alternative."

Outside transportation experts say, however, that rail consultant Parsons Brinkerhoff's methodology is so flawed the entire claim should be disregarded.

"The rail authority's analysis does not account for the roadway and airport work investment that will be required both with and without high speed rail," the Orange County Transportation Authority told the rail agency in a letter late last year. In November, the nonpartisan Legislative Analyst's Office questioned the study as well, saying the $171-billion estimate is not what the state would otherwise spend to address intercity transportation demand.

The city of Burlingame, which is near San Francisco International Airport, weighed in too. "The astounding figure is completely divorced from any reality over the next 50 years," city officials wrote urging the authority to stop using the number. Madanat said the rail authority has rebuffed offers to have UC Berkeley, UC Irvine and UC Davis, which have among the top five university transportation departments in the nation, help analyze the bullet-train system.

Instead, the rail authority has relied heavily on New York-based Parsons Brinkerhoff, a contractor that helped fund the political campaign for the $9.9-billion bond measure passed by voters in 2008. Although the rail authority has more than two dozen employees, Parsons controls 108 people working on the project.

"You have a tremendous conflict of interest," said Elizabeth Goldstein Alexis, co-founder of the watchdog group Californians Advocating Responsible Rail Design. "You can't see where the authority ends and the private consultants begin because they are so intertwined. It is extraordinary the institutional conflicts of interest that exist all over this project."

But Richard defended Parsons' role, saying, "They performed the analysis, which was an honest and realistic estimate of the project's costs -- not a policy justification of the project." He added that the alternative analysis represents a standard way that transportation projects are evaluated.

Nonetheless, Parsons does not answer the question of how much high-speed rail would reduce future investments in roads, public transit and airports, which other experts say is a more relevant guide to its value.

Caltrans predicts that traffic on Interstate 5 and California 99 in the Central Valley will double over the next 25 years. But agency officials say they have not scaled back plans to make highway improvements in the state's agricultural heartland because of the high-speed rail project. Not until the rail system is built and actually reduces traffic on both roads would Caltrans adjust its investment strategy, officials said.